The present invention relates to speaker assemblies for personal use such as in mobile terminals and, more particularly, to dual-diaphragm speaker assemblies.
Manufacturers and designers of personal electronic devices, such as cellular radio telephones, frequently seek to reduce the overall dimensions of such devices while maintaining attractive style characteristics for the devices. One consequence of the reduced size for such devices that include a speaker is that less space may be available for the speaker. Furthermore, a variety of audio signal generation capabilities may be desired in such personal electronic devices including buzzers, voice signal generation and/or music or other audio signal reproduction and playback.
For audio performance in wireless telephony, it is known to use a speaker having relatively uniform frequency characteristics in the 300 hertz (Hz) to 3400 Hz voice frequency band. Where music or other complex signals are provided by the device, a speaker with a frequency range providing a bandwidth up to at least 8000 Hz may be used. In addition, higher sound level alert signals may be provided in various personal electronic devices.
As the space available for the hardware supporting the audio signal generation capabilities decreases in the personal electronic devices, it may become more difficult to support multiple sound emitting output devices and the space available for each such device may become smaller. Furthermore, increased functionality in such personal electronic devices may require more of the reduced available space to be utilized for other functionality of the device. A reduction in the size of the audio output devices may increase the difficulty of providing a desirable loudness level for signals, such as buzzer alert signals. In addition, to the extent features of the audio output device(s) are presented externally on the personal electronic device, the impact of those features on the appearance of the product and/or the flexibility to place such visible features at different locations on the device may become important.
One known type of speaker is a dual-diaphragm speaker, which includes two micro-speakers in a single housing. One speaker may be a receiver speaker with frequency characteristics suited for the voice frequency band and the other may be a speakerphone and/or loudspeaker with an extended frequency range for music and/or other polyphonic signals. A dual-diaphragm speaker is typically positioned in a personal electronic device with the receiver speaker ported (acoustically connected) to the front of the device (toward the user's ear) while the loudspeaker is ported to the back of the device (away from the user's ear). As a result, positioning of the dual-diaphragm speaker in the device may be limited. For example, placement on a printed circuit board of the personal electronic device may be precluded, as the printed circuit board may physically block the output of either the receiver speaker or the loudspeaker. In addition, user dissatisfaction may result if high acoustic levels from the loudspeaker are ported too close to a user's ear.